A new study on sushi has found that higher-end, restaurant-grade tuna sushi often has higher mercury levels than the cheaper tuna sushi found at local supermarkets. Researchers evaluated the DNA of various tuna species and came to the conclusion that varieties like blue fin akami and big eye tuna that typically have firmer flesh and are more visually appealing, are generally higher in mercury than other less expensive varieties.
According to the research, which appeared recently in the journal Biology Letters, the reason why higher-grade tuna often has higher mercury levels than other grades is because mercury tends to build up in muscle rather than in fat. This is why species like the blue fin toro, which is a fatty variety of tuna, typically has lower levels of mercury than bluefin akami and bigeye tuna, which are leaner varieties.
One exception was yellow fin tuna, which is lean but also low in mercury. Researchers believe that because this species is smaller than other varieties, eats less, and is generally killed at a younger age, it tends to accumulate less mercury than other varieties. Read more...
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